Going Halvesies

Objective

SWBAT use straight-edge and compass to construct a (segment) bisector and verify its properties. Students will understand how geometric objects may be defined in terms of other objects and identified using geometric notation.

Big Idea

What are the properties of a bisector? Students see for themselves--and find that a compass is an efficient instrument for comparing distances.

Make formal geometric constructions with a variety of tools and methods (compass and straightedge, string, reflective devices, paper folding, dynamic geometric software, etc.). Copying a segment; copying an angle; bisecting a segment; bisecting an angle; constructing perpendicular lines, including the perpendicular bisector of a line segment; and constructing a line parallel to a given line through a point not on the line.

Summarizing - Defining Geometric Objects

15 minutes

I ask students to get out their Guided Notes: Constructions/ Defining Geometric Objects. Now that we know what lines and circles are, we can define other objects--segments, rays, and arcs--with precision (MP6). We complete the final page of the notes: Defining Geometric Objects.

Displaying the guided notes with the help of an interactive whiteboard, I lead the class in completing the definitions and the examples. I encourage students to use straight-edge and compass to construct the diagrams, although this is not strictly necessary.

Guided Notes: Constructions/ Defining Geometric Objects - Key

Guided Notes: Constructions/ Defining Geometric Objects

Lesson Close and Homework

4 minutes

Team Size-Up

The lesson close follows our Team Size-Up routine. The prompt asks students to explain what constructions are and why we learn them. This essential question for the unit was answered in the notes.

Homework

Homework Set 2 problem #23 asks students to practice some of the constructions they have just learned. Problem #24 reviews algebra concepts (slope). In addition, I assign Portfolio Problem 2- Placing a Call, which students should now be able to answer completely.